That's because all most politicians care about is holding onto power by being re-elected. The Tweetmaister just sends out messages to see what will fly and what will fall and sink. Sensing something has to be done he has sent his daughter to determine what stance can be made about guns while expanding electorate base and keeping the one he has.
Your post above is the truth. Other presidents sent up trial ballon via leaks to the Wapo or NYT, Trump tweets to buy time to figure out what to do. I think that the 2A is more or less a sideshow for him (and most Republican presidents aside from maybe Reagan) with the economy and reorganizing global trading patterns being his number one focus. On the other hand, he is smart enough to be persuaded by enough adamant opposition if he thinks it will cost him reelection.